1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a printer which forms an image on a recording material.
2. Description of the Related Art
Full color image forming apparatus adopting an electrophotographic type is advancing in recent years. A color image forming apparatus mounted with four or more process cartridges including a photosensitive drum is being widely used.
Such color image forming apparatus adopting an intermediate transfer type is being widely used to reduce the size of the apparatus main body and to eliminate image defects due to the type of recording material such as heavy paper. In such apparatus, the image created with four process cartridges is primary transferred to the intermediate transfer belt, and the toner image is secondary transferred to the recording material at a secondary transfer portion.
Recently, the arrangement of the intermediate transfer belt and the process cartridges widely uses the configuration of first arranging the intermediate transfer belt in the horizontal direction with the conveying direction of the recording material as the longitudinal direction, and arranging four process cartridges in line at the lower surface of the belt. According to such arrangement, the time until the secondary transfer of the toner image created in the primary transfer is reduced, and at the same time, the distance from the process cartridges to the secondary transfer portion is reduced, and in consequence, the printing time can be reduced (Japanese Patent Application Laid-Open No. 2003-287939).
The replacement of an image creating unit including a plurality of process cartridges described above will now be described.
First, a first prior art example is illustrated in FIG. 10. In an image forming apparatus main body 600, an intermediate transfer belt 601 and a transfer frame 602 supporting the intermediate transfer belt 601 are moved in the direction of an arrow R1, that is, upward so that the intermediate transfer belt 601 moves away from the photosensitive drums 604 in the process cartridges 603. The process cartridges 603 are thereafter pulled out in the P1 direction towards the front of the main body to be replaced.
In the above configuration, a pressurizing/pressure releasing mechanism for moving away/contacting the intermediate transfer belt 601 and the transfer frame 602 with respect to the photosensitive drums 604 is required. When detaching the intermediate transfer belt 601, the intermediate transfer belt 601 and the transfer frame 602 supporting the same are moved in the direction of the arrow R1, and a transfer roller or a conveyance roller (not shown) arranged facing the intermediate transfer belt 601 are evacuated in the direction of the arrow R2. The intermediate transfer belt 601 is then pulled out in the P1 direction towards the front of the main body. The damages on the components involved in the pull-out operation are thereby prevented. The pressurizing/pressure releasing mechanism for moving away/contacting the conveyance roller with respect to the intermediate transfer belt 601 is required in such configuration.
The replacing configuration of the intermediate transfer belt 601 and the process cartridges 603 of the prior art example is as follows. Since the pressurizing/pressure releasing mechanism of the conveyance roller with respect to the intermediate transfer belt 601 is required in addition to the pressurizing/pressure releasing mechanism of the intermediate transfer belt 601 with respect to the process cartridges 603, the configuration becomes complicating and the cost increases. Furthermore, such configuration is a disadvantage in terms of the size of the apparatus main body since the evacuation space for the intermediate transfer belt 601 and the evacuation space for the conveyance roller, which are not used other than in time of replacement, are required.
A configuration of contacting/moving away the conveyance roller and the intermediate transfer member by handle operation without arranging a pressure releasing mechanism is disclosed in Japanese Patent Application Laid-Open No. 2004-20691. In the relevant publication, a pull-out lever of the intermediate transfer unit cannot be completely unlocked unless a door 40 arranged at the side of the image forming apparatus is opened, as illustrated in FIG. 11. Such configuration prevents the intermediate transfer member from being pulled out with the conveyance roller and the intermediate transfer member in a contacting state.
However, such configuration requires the user himself/herself to open the side door, which increases the working step, and moreover, requires an unlocking unit 50, which increases the number of components.